Mapping of asperities and estimation of spatiotemporal distribution of interplate slip

粗糙体测绘和板间滑移时空分布估计

基本信息

批准号：
15204037
负责人：
HASEGAWA Akira
金额：
$ 26.21万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

项目摘要

In this research, we have been aiming to analyze details of lock and slip on the plate boundary under the Pacific Ocean in NE Japan and to understand the generation mechanism of interplate earthquakes. The main research contents are: 1. analysis of repeating earthquakes, 2. analysis of source process of medium ＆ large earthquakes based on broadband seismic waveform data, 3. GPS data analysis, 4. research on the property of asperities by using numerical simulation.According to the result of 1. analysis of repeating earthquakes, we successfully estimated the time variation of interplate slips around the rupture zone of the 2003 Tokachi-oki earthquake, by identifying the repeating earthquakes in all parts of the plate boundary under the Pacific Ocean from Hokkaido to NE Japan. As for the 2. analysis of source process based on seismic waveform data, we showed that the rupture area of Miyagi-oki earthquake (M7.2) on Aug. 16, 2005 is overlapped with the southeastern part of the rupture area … More of the 1978 Miyagi-oki earthquake. So, this means that the asperities of the 1978 earthquake located in the north and west part are left unruptured; our research pointed out the importance of continued and careful observation on this area. Moreover, we conducted reanalysis of aftershocks of Miyagi-oki earthquakes with magnitude >7 in 1930s, and found out that three asperities could have slipped separately, in three times, in the case of 1930s' Miyagi-oki earthquakes. With 3. GPS analysis, after 2005 Miyagi-oki earthquake, we detected the after slip which spread toward south of the rupture area of the event. This observation result corresponds with the result of seismic-waveform inversion analysis; the northern and western asperities are left unruptured. The result of 4. numerical simulation analysis shows that, in order to explain the propagation velocity of the after slip observed in the deep plate boundary close to land, pore pressure around the plate boundary should be extremely large. On the other hand, in order to explain the propagation velocity of the after slip observed in the shallow plate boundary close to the trench, large pore pressure is not necessary like in the case above. These results suggest the depth variation in the amount of water supplied to the plate boundary, which was caused by dehydration reaction, or the depth variation in coefficient of permeability around the plate boundary.As mentioned above, through this research, we have achieved substantial results to enhance understanding of the generation mechanism of interplate earthquakes. Less

在本研究中，我们旨在分析日本东北部太平洋下板块边界的锁定和滑移细节，了解板间地震的发生机制。主要研究内容是：1.重复地震分析，2.基于宽带地震波形数据的中大地震震源过程分析，3.GPS数据分析，4.利用数值模拟研究凹凸体的性质。根据1.重复分析的结果通过识别从北海道到日本东北部的太平洋板块边界所有部分的重复地震，我们成功地估计了 2003 年十胜冲地震破裂带周围的板间滑动的时间变化。根据地震波形数据对震源过程进行分析，我们发现2005年8月16日宫城冲地震（M7.2）的破裂区域与1978年宫城冲地震的东南部地区，这意味着1978年地震的北部和西部地区的凹凸不平，我们的研究指出了继续仔细观察的重要性。此外，我们对 1930 年代宫城冲 7 级地震的余震进行了重新分析，发现三个凹凸不平可能分别滑动。 3. 3. GPS分析，2005年宫城大地震后，我们检测到了向事件破裂区域以南扩展的后滑移。 4. 数值模拟分析结果表明，地震波形反演分析结果表明，北部和西部的粗糙体未破裂。在靠近陆地的深部板块边界观察到的滑移后，板块边界周围的孔隙压力应该极大。另一方面，为了解释在靠近海沟的浅部板块边界观察到的后滑移的传播速度，不需要像上面的情况那样大的孔隙压力。这些结果表明由脱水反应引起的供给到板块边界的水量的深度变化，或者板块边界周围的渗透系数的深度变化。如上所述，通过本研究，我们取得了增强对板间地震发生机制认识的实质性成果较少。